Catfish (order Siluriformes) are a diverse group of fish. Named for their prominent "barbels", which give the image of cat-like whiskers, they are found in freshwater environments of all kinds, with species on every continent except Antarctica. Some species from the families Ariidae and Plotosidae are also found in marine environments. They feature some of the smallest known vertebrates, including the candiru(a small fish that will swim into the penis or vagina of a swimmer, and latch on inSIDE. Often, with fatal consequences), the only vertebrate parasite to attack humans, as well as Pangasius gigas, the largest reported freshwater fish. There are armour plated types and also naked types, but they do not have scales. Not all catfish families have barbels; what defines a fish as being in the Siluriformes order are certain features of the skull and swimbladder. Catfish belong to a superorder called the Ostariophysi, which also includes the Cypriniformes, Characiformes, and Gymnotiformes (although some place Gymnotiformes as a sub-order of Siluriformes). As of 2005 there are 37 catfish families, and around 2000 species have been described, although this number is in constant flux due to taxonomic work on the order.

In June, 2005, researchers named the 37th family of catfish, Lacantuniidae, only the third new family of fish distinguished in the last 70 years (others being the coelacanth in 1938 and the megamouth shark in 1983). The new species in Lacantuniidae, Lacantunia enigmatica, was found in the Lacantun river in Chiapas, Mexico.

Catfish have no scales. All catfish, except members of Malapteruridae (electric catfish), possess a strong, hollow, bonified leading ray on their dorsal and pectoral fins, through which a stinging protein can be delivered if the fish is irritated. In members of the family Plotosidae, and of the genus Heteropneustes, this protein is so strong it may hospitalize humans unfortunate enough to receive a sting.

Catfish range in size and behavior from the heaviest, the Giant Mekong Catfish (Pangasius gigas) in Southeast Asia and the longest Wels Catfish of Eurasia, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru (Vandellia cirrhosa).

The wels catfish (Silurus glanis) is the only native catfish species in Europe, besides the much smaller related Aristotle catfish found in Greece. Mythology and literature record wels catfish of astounding proportions yet to be scientifically proved. The average size of the species is about 1,2m-1,6m, and fish more than 2m are very rare. The largest specimens on record measure more than 2.5m in length and sometimes exeeded 100kg. The wels catfish was introduced to Britain, Italy, Spain, Greece and some other countries during the last century. The species has flourished in the warm lakes and rivers of Southern Europe. The River Po in Italy and the River Ebro in Spain are famous for huge wels catfish, which grow up to 2m. These habitats contain plenty of food and lack natural predators.

When looking for a catfish for your aquarium, we recommend you do some investigation as to the size the specimen you are looking at in the pet shop will reach. That 6 cm tiddler, could grown into a 1.5 metre giant.

Other relevant pages - Catfish

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